The increasing awareness of the importance of sterility in hypodermic devices, coupled with the continually increasing number of hypodermic injections given, has led to the advent of disposable syringes. The initial sterility and low cost of disposable syringes has led to the widespread use of these syringes and the preference for disposable syringes over the older reusable glass syringes that require sterilization before each use.
The disposable syringe, by its very nature, has spawned problems. The disposable syringe is cheap and disposable and controls on the inventory of a cheap and plentiful item tend to loosen while controls on discarded items have generally been lax. It is not uncommon for syringes, along with the attached needles, to find their way into unauthorized hands. The syringes may be reused without sterilization and thereby contribute to a problem they originally were designed to prevent, i.e. the spread of disease due to contamination.
An unfortunately common unauthorized use of syringes is associated with the use of illegal drugs. The common practice of sharing the syringe among drug users dramatically increases the risk of exposure to, and spread of, disease.
Hepatitis has long been associated with illegal drug use as it is spread among users of injectable drugs via contaminated hypodermic devices. Today it is known that the Human Immune Virus associated with AIDS is spread similarly. Indeed, the highest rate of infection of AIDS is now found in intravenous drug users and the infection rate is increasing.
Non-reusable syringes will not stop drug use but can prevent sharing of contaminated needles and thus help fight the spread of diseases such as AIDS.
Non-reusable syringes have been designed in the past; however, there are numerous shortcomings in these earlier versions. Non-retractable drive shaft or piston arrangements such as found in Butterfield, U.S. Pat. No. 4,493,703, require pre-filled syringes as the syringe may not be filled by the user in the conventional manner. Lip-and-catch mechanisms of many sorts have been proposed, however until the lip-and-catch engages, the drive shaft and piston may retract and reuse is possible. Hesse, U.S. Pat. No. 4,731,068 requires a catch to be fixedly mounted and engage a slidable sheath thus requiring additional parts within the syringe, other embodiments require a plurality of cooperating parts that add to the complexity, assembly and cost of the syringe.
Owing to the problems or costs of the previous non-reusable syringes there has been no widespread acceptance and use of these devices in the medical community.